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Combating neglected tropical diseases: more than just drugs and vaccines

Neglected tropical diseases have been in the news this week. A big meeting at the World Health Organisation in Geneva has resulted in big pledges from the UK aid progamme and the Bill and Melinda Gates Foundation to banish the scourge affecting around a billion people worldwide. This is good news, and to be commended. But the focus of many of the announcements has been on drugs and vaccines – the technical solutions to prevention and cure. These are of course vital parts of the solution, but, as we have found in work on ‘sleeping sickness’ in southern Africa, as part of the ESPA-funded Dynamic Drivers of Disease in Africa project, they are not the whole story. Without a wider look at how politics and ecology interact in local situations, opportunities for disease or vector control may be missed, and money wasted.

Over the last few years, a team from the University of Zimbabwe and the Tsetse Control Branch of the Ministry of Agriculture of Zimbabwe has been looking at trypanosomiasis (a disease affecting animals and humans, when it’s called sleeping sickness), and the vector that carries it, the tsetse fly (see picture) in the Zambezi valley. We have been trying to unravel the complex puzzle that connects changing ecologies, disease and livelihood impacts, working as a cross-disciplinary team.

Despite decades of control efforts – from clearance of vegetation to wildlife extermination to aerial spraying of chemicals to baited traps (see this paper), the tsetse fly and trypanosomiasis, affecting both animals and humans, persists. And indeed in the last few years we have seen peaks in both human and animal forms. Not high, but definitely worrying – and devastating for those who are affected.

In our work, we trapped flies along transects, took blood from animals to look for parasites, examined habitat change from satellite imagery and talked to people in the villages. The question we had – why did the disease persist? – was a difficult one to answer. The official maps showed the tsetse ‘belt’ being kept to the south, into the Highveld. Control measures continued to some extent, and official reporting of trypanosomiasis, both animal and human, was highlighting very few cases.

Our tsetse fly surveys in Hurungwe district showed a peak of fly populations along the valley escarpment, with declining numbers of flies caught in our traps as you travel south away from the valley. Cluster traps located near villages and dips also showed a variable pattern. But overall tsetse fly populations (of different species) were low and relatively few were trapped. Why, if people complain about both animal and human trypanosomiasis? The answer came through an analysis of habitat change.

Abandoning very coarse grained images in favour of LANDSAT images with a higher resolution, we found a major shift in vegetation patterns over time, and particularly a noticeable fragmentation of habitat. Maybe the flies were residing in these fragmented habitat patches, and were not being picked up by the standard belt transects? This indeed proved to be the case.

When villagers analysed the satellite image maps of their area with us, they quickly pointed to particular patches where they knew flies were. The Mushangishe gorge, the pools near the Chewore river, the villages along the edge of the hunting area, the Makuti area, and so on. Some more focused trapping, sampling not randomly but purposively according to what people had indicated, showed that flies do still persist, even in heavily populated areas, but just in small patches.

So what about the disease-causing trypanosomes themselves? Analysis of 209 tsetse flies showed that nearly half were carrying trypanosomes following molecular DNA analysis at Edinburgh University. The most prevalent species was T. vivax (in 32% of flies), followed by T. brucei. This pattern was consistent across fly species (G. m. mortisans and G. pallidipes) and sex. Blood sampling of 400 cattle and 222 goats across 19 villages again showed a very heterogeneous pattern of presence, with trypanosomes (T vivax and T. brucei) being found in only four village sites, with presence in cattle ranging from 2-10 per cent. The places where infected animals were found tallied almost exactly with the places where local people had identified tsetse infested habitat patches. Perhaps surprisingly, given the reports of human trypanosomiasis, we found no evidence of T. b. rhodesiense in either fly or livestock samples; although of course this does not mean it is not present.

The puzzle had been (partially) solved. Tsetse flies and so trypanosomiasis (although no human sleeping sickness causing trypanosmes found as yet) persist because of the maintenance of particular habitat patches. Who gets sick (and whose animals) depends on who goes to these sites. Those most likely to get the disease, and those whose animals are the most susceptible, are mostly poor and marginalised people who must make a living on the edge of wildlife areas. They are hired herders or children of school age moving with animals deep into forested areas; they are groups of men going on hunting trips harvesting wild animals as a source of protein; they are women who forage in the forests, or who collect water from streams and rivers; and they are the new in-migrants into the area, offered land to settle and farm in the frontier areas, sometimes in the buffer zones of the national park and hunting areas.

As people put it to us “we are now fighting a guerrilla war against the tsetse”. They don’t exist along a ‘front’, an identifiable belt on a map as in the past, but in particular sites, which only particular people go to. Gender, age, occupation all make a big difference as to who gets potentially exposed. This has important implications for both monitoring (coarse grained satellite imagery, broad transects and random sampling are no use) and response (by the same token, generic, area-wide approaches make little sense). A more targeted approach, identifying particular patches, and particular people at risk is vital.

In addition, disease risk has to be understood through an appreciation of history, politics and social relations. Such people and their animals do not become sick by chance. Disease is often caused by what Paul Farmer calls ‘structural violence’, with disease being “the biological reflection of social fault lines”. Inequality, poverty, dispossession, alienation, lack of rights, and deep neglect by states results in disease impacts that are often not even noticed or recorded. The biological impacts of disease are thus reflected through politics, class, race and gender and changing landscape ecologies.

Tackling a neglected disease like sleeping sickness requires an understanding of ecology, social relations, politics and more. Expensive, magic bullet solutions through drugs or vaccines may not be the only answer – instead much simpler solutions may be on offer, if the social causes of disease are addressed and the ecological dynamics of disease risk understood. It is good that BGMF and DFID have pledged money; let’s hope it is used in an integrated ‘One Health’ approach, where complex solutions are developed for complex, multi-sectoral challenges.

The Dynamic Drivers of Disease in Africa work was supported by ESPA (Ecosystem Services for Poverty Alleviation) programme funded by NERC, ESRC and DFID, and the Zimbabwe study was led by Professor Vupenyu Dzingirai (CASS, UZ), working with William Shereni (Ministry of Agriculture), Learnmore Nyakupinda (Ministry of Agriculture), Lindiwe Mangwanya (UZ), Amon Murwira (UZ), Farai Matawa (UZ), Neil Anderson (Edinburgh University) and Ewan McLeod (Edinburgh University), among others.

This post was adapted from an earlier blog, and was written by Ian Scoones and appeared on Zimbabweland

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The political ecology of land and disease in the Zambezi valley

In addition to migration discussed in last week’s blog, the changing politics of land use in the Zambezi valley is another dimension that has affected the incidence of trypanosomiasis over time.

Over the last century, the people of Hurungwe have been subject to numerous external interventions. The Korekore were the original inhabitants of the area, prior to the waves of migration discussed last week. The reasons the Korekore are settled where they are today is a result of the massive engineering project of the Kariba dam, and the creation of the Mana Pools national park in the 1950s and 60s.

Colonial visions of modernity and the need for electricity to supply the growing industries and urban centres of Rhodesia resulted in a major eviction of people who had traditionally made a living along the Zambezi river. Colonial economic imperatives reshaped the landscape, and pushed people into new territories. In the subsequent decades, the Mana Pools area became a significant tourist attraction, generating revenues for the state and for elite ecotourism operators, as well as a symbolic site of ‘wild’ Africa for white residents of Rhodesia.

Surrounding the park a series of hunting/safari areas were established, and particularly after Independence, these became the location for high-end hunting operations. Some of these activities generated some employment for locals, but not much. Ecotourism and hunting was by and large the preserve of a white elite, and money did not find its way back into the local economy.

The Zambezi valley was a major front during Zimbabwe’s liberation war, with frequent incursions of fighters from Zambia and regular battles with the Rhodesian forces. In this period, tsetse control efforts were abandoned, and the fly encroached into once cleared areas. With peace and Independence in 1980, aid programmes supported clearance efforts once again, and the tsetse fly retreated. Combined with migration from other areas of the country (see last week’s blog), and the mid-1980s cotton boom, the habitat for tsetse flies also declined.

But there were countervailing drivers, encouraging an expansion of tsetse habitat too. From the late 1980s, Zimbabwe was at forefront of ‘community-based conservation’ and the CAMPFIRE programme became a world-famous experiment. Revenues from hunting were to go back to the community, and provide much needed support. But CAMPFIRE was premised on generating revenue from animals shot (or sometimes photographed) in the communal areas, where people lived. While providing an economic basis for conserving wildlife, it encouraged wild animals to be closer to people. And since such wildlife are significant hosts of trypanosomiasis, and their habitats the same as those of tsetse fly, the disease consequences of CAMPFIRE were potentially significant.

With the decline in hunting operations with the collapse of the economy and the failure of bankrupt Rural District Councils to share revenues, CAMPFIRE has declined in significance. But there is a new kid on the block, focused not on wildlife, but on carbon. A massively ambitious project – Kariba REDD – was established notionally over thousands of hectares, including in Hurungwe, and in our study area. Making use of international markets for carbon, and linking to the UN REDD programme (Reducing Emissions from Deforestation and Forest Degradation in Developing Countries), the project aimed to put a value on carbon, and reverse the decline in forested area across the Zambezi valley.

Through protecting – and indeed expanding – forests against a notional baseline, other values could be marketed, including an expanded trade in ecotourism and wildlife hunting. Like the interventions that went before, carbon is restructuring disease landscapes too. As carbon has acquired value, the project is increasing incentives both the plant and protect trees. These may expand the habitat of tsetse flies, including into the formerly cleared areas.

Understanding disease incidence, spread and risk requires looking at the underlying structural drivers. These are not just the proximate ones of changing climate, habitat, demography and so on, but can be traced back to much deeper causes. Whether these are the factors that drive migration or incentivise investments in hunting or carbon, these can be linked to wider political economy processes. These may often reach to the global political economy; way beyond the confines of the fields and forests of the Zambezi valley.

A political ecology of disease must therefore take these factors into account. Any appraisal of intervention – whether for forest protection, carbon sequestration, wildlife protection or infrastructure development – must look at these wider webs of power and influence. Without looking at the political drivers of disease, we may never understand underlying causes, or define the most appropriate interventions. As the blogs in this series have shown, ‘control’ interventions may miss their target, if wider questions of land access, migration, economic opportunity and the politics of competing land values are not addressed.

The Dynamic Drivers of Disease in Africa work was supported by ESPA (Ecosystem Services for Poverty Alleviation) programme funded by NERC, ESRC and DFID, and the Zimbabwe study was led by Professor Vupenyu Dzingirai (CASS, UZ), working with William Shereni (Ministry of Agriculture), Learnmore Nyakupinda (Ministry of Agriculture), Lindiwe Mangwanya (UZ), Amon Murwira (UZ), Farai Matawa (UZ), Neil Anderson (Edinburgh University) and Ewan McLeod (Edinburgh University), among others.

This post was written by Ian Scoones and appeared on Zimbabweland.

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Migration and changing disease dynamics in the Zambezi valley

 In last week’s blog, we saw how ‘structural violence’ and deep patterns of inequality and marginalisation, affected by patterns of social difference – of gender, age and ethnicity – have influenced who gets exposed to trypanosomiasis (just as is the case with other diseases, such as Ebola).

This week, the theme is continued, by looking at how migration into the area has created both dramatic land use change and changing patterns of vulnerability to different social groups. Migration has radically changed landscapes in the Zambezi valley over the past 30 years, as large numbers of new people moved into what were once sparsely populated areas.

As people have moved into the valley to farm – first cotton, now increasingly tobacco – they have cleared land for fields and homes. Initially animals suffered badly from trypanosomiasis, but this declined after a while, as cleared areas were created through intensive control efforts. The work of the Tsetse Control Branch, and projects such as the RTCCP, funded by the European Union, helped. But such control was always partial, and risks increased as people settled in new areas.

In the 1980s and 1990s people moved from the overcrowded communal areas to the south. Unable to make a living on shrinking land sizes and in the context of the absence of a substantial land reform programme. From the 1990s, following a structural adjustment programme that shrunk the economy and reduced job opportunities, people had to find other means of making a living, and migration to new lands was one response.

In the late 1980s I was living in Zvishavane district in the central-south of the country in a communal area. From our sample, several people made the move to go and settle elsewhere (in Gokwe, Muzarabani and beyond). They were relatively young men with their families who had been granted very small fields, and had greater ambitions. As employment opportunities shrunk, carving out a new life on the land frontier to the north was increasingly appealing. As the boom in smallholder cotton growing occurred, news travelled back, and more left.

On arrival, it was a harsh existence. New fields had to be cleared from pristine bush, wildlife were a constant threat, and the tsetse fly was ever-present in the newly settled areas, constantly threatening the health of both people and animals. Today, the settlers from 20-30 years ago are now established, have cleared land (and so tsetse flies), and many are currently prospering from the tobacco boom. Well connected to political elites, these now 50-60 year olds are mostly no longer part of the vulnerable population that they once were.

But today, a new group of migrants has arrived, and they are especially vulnerable to disease, again being pushed to a new fly-infested frontier. With land reform in 2000, the Karoi farms to the south of our study area were taken over, and transformed into land reform settlements. In this area, many well positioned political figures took over the large, (mostly) tobacco farms, although there were also subdivisions to create A1 farms for many more people.

In both cases, farm workers who had lived on these farms for generations, often in appalling conditions, were expelled in numbers. Thousands had to seek other alternatives to farm wage labour. A few had connections elsewhere in Zimbabwe, but many were second or third generation ‘foreign’ migrants, originally from Malawi, Mozambique or Zambia, with nowhere to go. They had been isolated through the form of ‘domestic government’ so well described by Blair Rutherford in these very sites, and were almost completely reliant on the white farm owner.

With the economy nose-diving due to a complex combination of gross economic mismanagement, capital flight and economic sanctions from western governments, after land reform many fled north to our study sites in the valley in search of land for farming, or for hunting and gathering. The local chiefs had already accommodated huge numbers of others in the previous years, where were these new arrivals to go? Eager to expand their territory and increase numbers under their rule (and so acquire increased remuneration from the government), they placed them along the frontier of the national park, and even, illegally, into the buffer area. Acting as a human and livestock shield for others in the now cleared core areas, they provided political and economic benefits to local elites, while in the process taking the brunt of disease impacts.

Thus the disease landscape has over time been radically restructured by migration, and the demand for land. Understanding disease is not just a biological-epidemiological task, but one that must take account of wider political economic factors – such as the state of the economy, opportunities for employment, land reform impacts and more. Diseases such as trypanosomiasis are always inevitably political.

The Dynamic Drivers of Disease in Africa work was supported by ESPA (Ecosystem Services for Poverty Alleviation) programme funded by NERC, ESRC and DFID, and the Zimbabwe study was led by Professor Vupenyu Dzingirai (CASS, UZ), working with William Shereni (Ministry of Agriculture), Learnmore Nyakupinda (Ministry of Agriculture), Lindiwe Mangwanya (UZ), Amon Murwira (UZ), Farai Matawa (UZ), Neil Anderson (Edinburgh University) and Ewan McLeod (Edinburgh University), among others.

This post was written by Ian Scoones and appeared on Zimbabweland.

 

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Fighting the fly: drivers of disease in the Zambezi valley

The battle against the tsetse fly in the Zambezi valley is a long and continuing one. The fly is the source of both animal and human trypanosomiasis – nagana in cattle, sleeping sickness in humans – and is one of the reasons why the valley has been only sparsely inhabited until recently.  But the relationship between the fly, livestock, wildlife and people appears to be changing, with new transmission dynamics unfolding, potentially with dangerous consequences.

A new project, led by the University of Zimbabwe, with the Tsetse Control Branch in Veterinary Services in the Ministry of Agriculture, and working with the STEPS Centre at Sussex and the Universities of Edinburgh and Southampton, is trying to get to grips with the ‘dynamic drivers of disease’ that affect who and what gets infected and where.

Conquering the fly and pushing back the fly belt was seen from the colonial era as one of the great civilising efforts of colonial development. Tsetse control was seen as a prime reason for intervention: clearing vegetation, exterminating wildlife, moving people, often in draconian ways. Yet others see the fly as the saviour of wilderness, and key to conservation of remote, biodiverse landscapes, protecting such areas from encroachment by people and their animals. The fly in other words is at the centre of the classic tussle between visions of civilisation and modernity and conservation and preservation, reflecting conflicting values, perceptions, politics and interests.

The social, ecological, political and economic consequences of the tsetse fly are therefore profound, raising fundamental debates about how people and disease interact in complex ecosystems. In his classic book, The Role of Trypanosomiases in African Ecology: A Study of the Tsetse Fly Problem“, published in 1971, John Ford – a scientists centrally involved in colonial control efforts – explored some of these debates, and challenged what he described as the ‘colonial doctrine’ of tsetse control, based on an ecological understanding of disease dynamics. Forty years on, the dilemmas of fly control persist today, with some important new contexts.

In our study area in Hurungwe district in Zimbabwe, a number of cases of human sleeping sickness have been confirmed in recent months. These are unusual in Zimbabwe, although reporting is often poor, so official data is misleading. When people become sick and die, the usual diagnosis is malaria. Scientists are wondering has something occurred in the ecology of the area to increase human infections? There are other puzzles too. Dissections of tsetse flies at the government’s Rukomichi research station, in the heart of the tsetse belt in the Mana Pools National Park, show very few T. brucei rhodesiense trypanosomes, the ones that cause the disease in humans. Yet blood samples taken from cattle outside the park, show much higher incidence. And now humans are dying too. What is going on?

The new research is trying to investigate. Is it changes in rainfall and climate patterns affect fly distributions and behaviour? Is it changes in vegetation and land use, influencing livestock-fly interactions? Is it changing settlement patterns, with people moving into wildlife areas, and coming into contact with wildlife disease hosts and fly vectors? Is it changes in wildlife movements, as they seek water and grazing outside the park? Is it changes in human behaviour and susceptibility as new people come to the valley in search of farm land for elsewhere in the country?

Unfortunately, we simply don’t know the answers to any of these questions, and so cannot suggest what disease control strategies might work. There has of course been masses of work on tsetse and trypanosomiasis in Zimbabwe, part of long-term research and development programmes. But much of this has been very targeted – on fly behaviour, chemical control, and trap design, for example. While this has been enormously important in developing effective, low-cost control approaches, it has often not looked at the underlying ecological, social and economic drivers. This holistic, integrated, cross-disciplinary perspective is of course not new. John Ford was a great advocate of this from the 1960s, but it is only recently that a ‘One Health’ approach to emerging (and in this case re-emerging) infectious diseases has become central to policy debates.

Our new research, working closely with colleagues in Zambia on the other side of the Zambezi, aims to come up with new perspectives on what is going on. It is an important, but difficult challenge, and one that requires dedicated cross-disciplinary science to tackle. Watch this space for some results over the coming few years.

This post was written by Ian Scoones and originally appeared on Zimbabweland

 

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